Re: Why dovetails?

> > Why dovetails? Three reasons 1) stability and accuracy thru

length

> and mass of high tolerance dovetail connection

2) The design

> inherently "locks" the two mating surfaces together eleminating the
> requirement of any other method of maintaining engagement of the

two

> surfaces.

3) surface area of the mating joint, distributing the load

> over a much larger area.
> >
> > Traversing a carriage etc. over lengths of any type geometry
> supported at both ends will produce an undesirable surprising

amount

> of deflection.



>
> /// We are discussing a home made machine. The original poster was

inquiring about the feasability of linear slides versus dovetail ways
for stability.


The short version is that if you take a 10 foot shaft and secure the
ends, the center will swign like a rope bridge. This happens at much
less movement with shorter rails, but happens nonetheless.

I've not heard of them referred to as "THK" a generic term, but there
are end supported and continous supported rails. The added support
from a very small base on a continuous will greatly reduce the
movement.

As for dovetails, in my opnion, they are are on the high end of home-
brew. To get a good fit, one must machine them, and/or hand
scrap. very difficult for a beginner.

Also, dovetails have a much larger surface area as compared to linear
bearings. Linear bearings offer signifigantly less friction,
espically when way oil is cold.

Dave